Exhaust gas post processing method

ABSTRACT

An exhaust gas post processing method may include determining whether a driving condition is included in an area for monitoring a rapid-heat-up (RHU) logic process that is used to quickly raise a temperature of exhaust gas passing an exhaust line, detecting on/off signal that performs or stops the rapid-heat-up logic process, determining whether an injection signal for performing the rapid-heat-up logic process is activated or not, detecting error of components for performing the rapid-heat-up logic process, and detecting the temperature of the exhaust during the rapid-heat-up logic process and comparing the detected temperature with a modeled value. 
     Accordingly, malfunction of the rapid-heat-up logic process is prevented before hand to realize the rapid-heat-up logic process securely, and the malfunction by the error signal is informed to the driver such that the on board diagnosis function is improved.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority of Korean Patent Application No. 10-2010-0120936 filed Nov. 30, 2010, the entire contents of which is incorporated herein for all purposes by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust gas post processing method that utilizes a rapid-heat-up (RHU) logic process to quickly raise a temperature of exhaust gas so as to activate catalyst that reduces harmful material included in the exhaust gas.

2. Description of the Related Art

A diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR) unit are sequentially disposed along an exhaust passageway in a predetermined order in a conventional exhaust purification device.

The exhaust gas of the engine passes the diesel oxidation catalyst, the diesel particulate filter, and the SCR unit sequentially and harmful materials therein is eliminated.

That is, the diesel particulate filter traps particulate matters (PM) included in the exhaust gas, the diesel oxidation catalyst oxidizes carbon monoxide and hydrocarbon included in the exhaust gas to carbon dioxide, and the SCR unit reduces nitrogen oxide included in the exhaust gas to nitrogen gas.

Meanwhile, the exhaust gas temperature of an upstream side of the SCR unit is to be higher than 200° C. so as to make the nitrogen oxide actively react with the reducing agent. However, since the SCR unit is disposed at a rear end portion of the exhaust passageway, a comparably long time is necessary until the exhaust gas temperature of a front side of the SCR unit reaches a temperature higher than 200° C.

Accordingly, the nitrogen oxide included in the exhaust gas is hardly reduced to be exhausted outside until the exhaust gas temperature of a front side of the SCR unit reaches 200° C.

Meanwhile, a rapid-heat-up (RHU) logic process for quickly raising the exhaust gas temperature has been gradually applied so as to quickly heat the catalyst, and it is necessary to determine a driving condition for performing the rapid-heat-up logic process and to detect an error thereof.

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

The present invention has been made in an effort to provide an exhaust gas post processing method having the advantages of performing a rapid-heat-up logic process for quickly raising a temperature of exhaust gas and having on board diagnosis function determining whether the rapid-heat-up logic process is performed normally.

An exhaust gas post processing method may include determining whether a driving condition requires monitoring a rapid-heat-up (RHU) logic process that is used to quickly raise a temperature of exhaust gas passing an exhaust line, detecting on/off signal that performs or stops the rapid-heat-up logic, determining whether an injection signal for performing the rapid-heat-up logic process is activated or not, detecting error of components for performing the rapid-heat-up logic process, and detecting the temperature of the exhaust during the rapid-heat-up logic process and comparing the detected temperature with a modeled value.

The exhaust gas post processing method may include outputting an error signal in a case that the detected temperature that is raised by the rapid-heat-up logic process gets out of the modeled value.

The exhaust gas post processing method may include accumulating the error signal, and storing the accumulated value and activating a rapid-heat-up logic warning lamp, for example, a malfunction indicator lamp (MIL), if the accumulated value exceeds a predetermined value.

The driving condition for performing the rapid-heat-up logic process that requires entering into the rapid-heat-up logic process, and the condition for entering into the rapid-heat-up logic process is determined based on an atmospheric pressure, a vehicle speed, an engine speed, an intake air temperature, a coolant temperature, a gear speed, and a fuel injection amount.

If the condition for entering into the rapid-heat-up logic is satisfied, a post injection amount for performing the rapid-heat-up logic process is determined based on the engine speed and the fuel injection amount to inject the fuel.

The component includes an injector injecting the fuel and a temperature sensor detecting the temperature of the exhaust gas in a step of the detecting the error of the component.

A diesel oxidation catalyst that oxidizes harmful materials included in the exhaust gas, a diesel particulate filter that filters particulate matters included in the exhaust gas, a dosing module that injects reducing agent into the exhaust gas passing the exhaust line, and a selective catalyst reduction unit (SCR) that uses the reducing agent injected by the dosing module to reduce/oxidize nitrogen oxide included in the exhaust gas are sequentially disposed on the exhaust line.

Temperature sensor detects temperatures of a rear side of the engine, a front side of the diesel oxidation catalyst, a front side of the diesel particulate filter, and a front side of the selective catalyst reduction unit.

In the exhaust gas post processing method according to the present invention as described above, malfunction of the rapid-heat-up logic process is prevented before hand to realize the rapid-heat-up logic securely, and the malfunction by the error signal is informed to the driver such that the on board diagnosis function is improved.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary exhaust gas post processing system according to the present invention.

FIG. 2 is a schematic flowchart of an exemplary exhaust gas post processing method according to the present invention.

FIG. 3 is a detailed flowchart showing an exemplary exhaust gas post processing method according to the present invention.

FIG. 4 is a graph showing a temperature of exhaust gas and a diagnosis function thereof in a condition that an exemplary rapid-heat-up logic process is performed according to the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of an exhaust gas post processing system according to various embodiments of the present invention.

Referring to FIG. 1, an exhaust gas post processing system includes an engine 100, an injector 110, a control unit 120, an exhaust line 130, a diesel oxidation catalyst 140, a diesel particulate filter 150, a dosing module 160, a mixer 170, a selective catalyst reduction unit 180, and a temperature sensor, which may include one or more sensors, for example, T3, T4, T5, T6, and/or T7.

The injector 110 is provided on the engine 100 and the injector 110 injects fuel into a cylinder to perform a post injection for a rapid-heat-up (RHU).

The exhaust gas of the engine 100 sequentially passes the diesel oxidation catalyst 140 of the exhaust line 130, the diesel particulate filter 150, the mixer 170, and the selective catalyst reduction unit 180 to be exhausted to the outside through a muffler.

The temperature sensor T6 and T7 detects a temperature of the exhaust gas flowing into the diesel oxidation catalyst 140, a temperature of the exhaust gas flowing into the diesel particulate filter 150, and a temperature of the exhaust gas flowing into the selective catalyst reduction unit 180.

The control unit 120 uses a driving condition of the engine 100 and the exhaust gas temperature flowing the exhaust line 130 to determine whether a rapid-heat-up logic process is to be performed or not, and if the condition for performing the rapid-heat-up logic is satisfied, a normal injection and a post injection are performed through the injector 110.

Further, the control unit 120 uses a driving condition of the engine 100 and the exhaust gas temperature flowing the exhaust line 130 to stop the rapid-heat-up logic or not to start the rapid-heat-up logic.

FIG. 2 is a schematic flowchart of an exhaust gas post processing method according to various embodiments of the present invention, and FIG. 3 is a detailed flowchart showing an exhaust gas post processing method according to various embodiments of the present invention.

Referring to FIG. 2, it is determined in a step S200 whether or not a monitored condition requires a rapid-heat-up function, for example, the RHU logic process.

Here, it is determined whether or not a driving condition warrants the rapid-heat-up logic process.

Further, the monitoring of the rapid-heat-up function can itself be considered a condition that may warrant the rapid-heat-up function logic process be performed.

More particularly, in a {circle around (1)} of FIG. 3, the control unit 120 detects an atmospheric pressure, a vehicle speed, an engine speed, an intake air temperature, a coolant temperature, a gear speed, a fuel injection amount, and an exhaust gas temperature (T6 or T7), determines whether the rapid-heat-up function is to be performed or not, and monitors the condition that the rapid-heat-up function is being performed.

It is determined whether the rapid-heat-up function is ON or OFF in a S210 of FIG. 2, and it is determined whether an injection signal for performing the rapid-heat-up function is activated or not in a S220.

The injection signal includes an operating signal that is transferred from the control unit 120 to operate the injector 110 such that a post injection is performed.

An error of the components for performing the rapid-heat-up logic is detected in a S230. Referring to {circle around (4)} of FIG. 3, the injector 110 and the temperature sensor (T3 to T7) are used so as to perform the rapid-heat-up, if the injector 110 or the temperature sensor (T3 to T7) malfunctions or breaks down, the control unit 120 generates an error signal of the components for the rapid-heat-up.

In a S240, a temperature of the exhaust gas is detected during the rapid-heat-up, the detected temperature is compared to a modeled temperature, and it is determined whether the temperature of the exhaust gas ranges in a predetermined temperature area.

If the rapid-heat-up function is over in a S250, the monitoring ends to output result thereof. Referring to {circle around (5)} and {circle around (6)} of FIG. 3, the rapid-heat-up function is evaluated by detecting the temperature of the exhaust gas through the temperature sensor.

More particularly, if the exhaust gas temperature exceeds a predetermined temperature range during the monitoring, an error signal is generated, the generated error signal is counted, and the counted number is stored.

Further, if the counted number exceeds a predetermined or modeled value, it is determined that the rapid-heat-up logic is abnormally operated to activate a warning lamp, for example, a malfunction indicator lamp (MIL).

FIG. 4 is a graph showing a temperature of exhaust gas and a diagnosis function thereof in a condition that a rapid-heat-up logic process is performed according to various embodiments of the present invention.

Referring to FIG. 4, a horizontal axis indicates time, and a vertical axis indicates a temperature of the exhaust gas flowing into the selective catalyst reduction unit 180.

As shown, a range of the RUH model temperature 400 is set by a predetermined map data, and a graph of the exhaust gas temperature 410 flowing into the selective catalyst reduction unit 180 is formed during the ON condition of the RHU. Further, a graph of the exhaust gas temperature 420 is formed during the OFF condition of the RUH.

In addition, a modeled temperature 430 of the exhaust gas is formed by a driving condition of the engine and the rapid-heat-up logic, and an error signal 440 is generated, if a temperature 410 exceeds the modeled temperature 430 and the predetermined temperature range 400.

The control unit 120 counts the error signal and stores the counted number, and if the counted number exceeds a predetermined or modeled value, activates a warning lamp (MIL).

For convenience in explanation and accurate definition in the appended claims, the terms “front” or “rear”, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

1. An exhaust gas post processing method, comprising: determining whether a driving condition requires a rapid-heat-up (RHU) logic process to quickly raise a temperature of exhaust gas passing through an exhaust line; detecting an on/off signal that performs or stops the rapid-heat-up logic process; determining whether an injection signal for performing the rapid-heat-up logic process is activated or not; detecting an error status of one or more components for performing the rapid-heat-up logic process; and detecting the temperature of the exhaust during the rapid-heat-up logic process and comparing the detected temperature with a modeled value.
 2. The exhaust gas post processing method of claim 1, further comprising: outputting an error signal when the detected temperature that is raised by the rapid-heat-up logic process various from the modeled value.
 3. The exhaust gas post processing method of claim 2, further comprising: accumulating the error signal, and storing the accumulated value and activating a rapid-heat-up logic warning lamp, if the accumulated value exceeds a predetermined value.
 4. The exhaust gas post processing method of claim 1, wherein the driving condition for entering into the rapid-heat-up logic process is determined based on an atmospheric pressure, a vehicle speed, an engine speed, an intake air temperature, a coolant temperature, a gear speed, and a fuel injection amount.
 5. The exhaust gas post processing method of claim 4, wherein if the condition for entering into the rapid-heat-up logic process is satisfied, a post injection amount for performing the rapid-heat-up logic process is determined based on the engine speed and the fuel injection amount to inject the fuel.
 6. The exhaust gas post processing method of claim 1, wherein one of the components includes an injector injecting the fuel and a temperature sensor detecting the temperature of the exhaust gas in a step of the detecting the error of the component.
 7. The exhaust gas post processing method of claim 1, wherein: a diesel oxidation catalyst oxidizes harmful materials included in the exhaust gas; a diesel particulate filter that filters particulate matters included in the exhaust gas; a dosing module that injects reducing agent into the exhaust gas passing the exhaust line; and a selective catalyst reduction unit (SCR) that uses the reducing agent injected by the dosing module to reduce/oxidize nitrogen oxide included in the exhaust gas are sequentially disposed on the exhaust line.
 8. The exhaust gas post processing method of claim 7, wherein: a temperature sensor detects temperatures of a rear side of the engine, a front side of the diesel oxidation catalyst, a front side of the diesel particulate filter, and a front side of the selective catalyst reduction unit. 